Investors have some good reasons to look forward to the next earnings report from Costco Wholesale (NASDAQ:COST). The retailing giant's last few monthly sales reports have painted a bright picture for growth through August, and that's been confirmed by recent outlook comments from peers such as BJ's Wholesale Club (NYSE:BJ) and Kroger.

But that positive demand environment has set the bar fairly high for Costco to announce a strong finish to its fiscal year while projecting further solid gains ahead. With that big picture in mind, let's look at the key trends to watch for in Costco's report set for Thursday, Sept. 24.

An employee restocking fresh produce.

Image source: Getty Images.

Market share updates

Costco reports monthly sales results, and so investors already know that comparable-store sales rose 14% in the core U.S. market this quarter, which runs through late August. That result stacks up well against Walmart's (NYSE:WMT) Sam's Club and its 13% boost through July. Regional warehouse club BJ's, meanwhile, grew comps by 24% through early August.

Kroger was the most recent competitor to announce its quarterly results, saying in mid-September that sales through early August were up 15% to mark just a slight slowdown from the prior quarter's 19% surge. Thursday's report will add context to Costco's expansion pace by revealing details like customer traffic and average shopper spending.

Membership fees

Costco is a membership club first and a retailer second, and so its club fees are critical to watch for signs of improving profit power. That metric rose 5% last quarter and is up about 6% over the first three quarters of the fiscal year.

The chain needs solid growth here, which comes from both a rising subscriber base and a higher penetration of executive level memberships, to keep prices low and protect its share against rival retailers. BJ's and Kroger are each enjoying a surge of profits that the chains intend to pour mostly back into the business. Robust membership fee income is Costco's surest defense against competitive threats like these.

Renewal rates

Executives revealed in late July that Costco's renewal rate had held near a record high. Fully 91% of its shopper base chose to renew its annual memberships during the early days of the pandemic. CFO Richard Galanti warned that most of the impact of COVID-19 on that key metric wouldn't show up until later quarters, and Thursday's report will be Wall Street's first opportunity to see how that trend has shifted during this volatile period for the industry.

Another quarter of over 90% renewals would point to a strong start to fiscal 2021, which began in September. Sure, sales gains will slow from the 9% surge the retailer notched in the year that just closed. But Costco seems set to continue its long track record of steadily winning market share.

Customers are busy consolidating their shopping trips to just a few of their favorite stores while the COVID-19 threat remains. Costco's wide product selection and value-focused pricing are even more valuable assets in this new retailing environment.